Hundreds of thousands of South Koreans took to the streets in Seoul on Saturday in rival rallies which exposed a sharply divided nation over the ouster of President Park Geun-hye.

Park's critics held their last and 20th candlelight demonstration in Gwanghwamun Square in the city center in the evening. They wrapped up their five-month weekly protests, which led to the Constitutional Court's ruling Friday to uphold her impeachment over a massive corruption scandal.

Calling it the victory of the people, the participants called for Park's arrest and punishment. The prosecution has named Park an accomplice to confidante Choi Soon-sil in extorting money from Samsung Group.

They also called for the ouster of Acting President Hwang Kyo-ahn who played a central role in the Park administration and refused to extend an independent investigation into the scandal.

The organizers announced a statement laying out their demands for reforms for democracy, equality and fairness. They peacefully marched toward the presidential office Cheong Wa Dae, where Park is still staying despite her dismissal.

The organizers estimated about 650,000 protesters gathered in central Seoul, while protests in other cities drew about 50,000 people. They said that an accumulated 16 million people have participated in candlelight vigils since the first rally last October.

The organizers said they will gather together on March 25 and April 15 to commemorate the third anniversary of a 2014 ferry sinking that killed more than 300. Park has been criticized for the botched response to the disaster.

South Korean protesters watch a firwork display at Gwanghwamun Square in Seoul on March 11, 2017, one day after the Constitutional Court's ruling to uphold the impeachment of President Park Geun-hye. (Yonhap)

Meanwhile, the supporters of Park held their own protest in front of nearby Deoksu Palace in the evening demanding the court ruling be nullified. The organizers of the pro-Park demonstration claimed about 700,000 people joined their rally and waved the Korean flag.

The pro-Park group refused to accept the court's decision which they said trampled on justice and truth. The organizers said they will form a new political party for a people's revolution to restore justice, law and democracy.

Hours before the rally, dozens of Park supporters threw combustible substances and sprayed fire extinguishers at a police station in an angry reaction to the police's move to tighten security around their protest site. Four of them were taken into custody for investigation.

Protests by Park supporters are becoming increasingly violent. Since the court's ruling to dismiss Park on Friday, three people have died, reportedly from injuries they sustained during rallies in the capital.

Mindful of deepening national division, Acting President and Prime Minister Hwang Kyo-ahn has urged the nation to accept the court's decision and work together to end divisions and restore national unity. (Yonhap)

A group of pro-Park protesters march in a rally near Deoksu Palace in central Seoul on March 11, 2017, one day after the Constitutional Court's ruling to uphold the impeachment of President Park Geun-hye. (Yonhap)